Washingtonians who live close to the National Zoo know all too well about gibbon songs. The small apes begin calling out to one another every morning at dawn and again throughout the day whenever they switch locations, get a lot of visitors or just feel like hollering.
It turns out that some of those songs might have distinctive characteristics similar to accents, according to a recent study in the journal BMC Evolutionary Biology.
After analyzing samples from more than 400 gibbon songs, researchers at the German Primate Center in Goettingen found that the calls can be used to identify which species of gibbon is singing as well as the area it's from. The scientists were able to distinguish the sounds of apes from various parts of the dense rain forests of Cambodia, Vietnam and Laos, where gibbons live in the wild.
However, people living near the zoo won't be able to detect the regional differences without sophisticated sound analysis software; not even Lisa Stevens can do that, and she's been working with the zoo's gibbons for 33 years. Stevens, the zoo's curator of primates, says the songs of the six gibbons living there are very similar. The zoo has four white-cheeked gibbons: two males that were born there and two females that were brought in from the wild, probably from Vietnam. The females are "geriatric" now at ages 41 and 43, Stevens says. They came to the United States in the late 1960s or early 1970s from markets in Southeast Asia where people were selling them as pets.
The zoo also has two siamangs from the Malay peninsula.
Stevens was not surprised at the study's results, because regional variation in color and pattern of gibbon coats has already been established. She expects that there are also behavioral differences among gibbons from different regions. Gibbons sing to define their territory and to find mates, but Stevens suspects there's more content than that. "We're just scratching the surface of the information that they're communicating in gibbon calls," she said.
Saslow, Rachel. 2011. "Gibbon songs have regional accents, says new study". Washington Post. Posted: February 28, 2011. Available online: http://www.washingtonpost.com/wp-dyn/content/article/2011/02/28/AR2011022805262.html
Picture: Mehgan Murphy / National Zoo